Contactor / relay

[breezer]

nope, that can't be right, look at the image above (not wishing to teach you to suck eggs you understand) but the coil pulls in a lever which has a hammer which stickes the gong,, its not being pulled inside, but its still a solenoid

not to be confused with

as this is an android

then there is

which is ann droid

 

[ricicle]

I think you'll find that lever is attached to an iron armature which gets pulled into the coil.

 

[breezer]

yes, (well it gets very close to it) but the coil is a solenoid

 

[Space cat]

"Solenoid" is the generic name for a long(ish) coil whether there's a core in it or not. Confusion arises because devices with moving cores designed to perform some mechanical operation tend to be called solenoids. Electric bells can be made with fixed cores or moving cores. Ours has a moving core which hits one bell tube then rebounds onto the other when you let go of the switch.

As a rule, relays have fixed cores and contactors have moving cores but the biggest difference is in the contacts. What nobody seems to have mentioned yet is that most contactors, at least all the ones I've ever seen, are double break. That is to say that when they open there are two gaps per pole.

Although the two devices perform the same function their construction is different. The relay has a fixed core which acts on a moving armature. This in turn operates the contacts of which there can be many, both NO and NC. Contact ratings vary widely and contact material is chosen to suit.

The contactor has a core in two halves which, when they close, form a complete magnetic circuit. In effect it's a transformer core cut through the middle. One half is fixed and the other carries the contact bars. These bars have a contact on each end and they are pulled down onto two fixed contacts, one on each side. The connections are made to the fixed ones. They are invariably NO and designed for heavy current, the favoured material being silver cadmium oxide. You won't find many gold plated ones!

Another common feature of contactors is that coils and contacts can be replaced. Often they don't even come with coils. You buy the coils separately and you get a choice of operating voltages. Coils of equal size and power consumption have the same MMF (amp turns) so you can mix and match. Extra contacts of lower power rating can be added on top or to either side. These can be NO or NC. Time delay contacts are also available.

 

[tim west]

100A relays even

100 amp relay